Grease composition



GREASE COMPOSITION Morton Fainman, Chicago, 11]., and Reuben A. Swenson,

Whiting, Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana No Drawing. Application November 29, 1954, Serial No. 471,878

9 Claims. (Cl. 25233.6)

and a lever system for applying the load to the test block.-

Timken values obtained by subjecting the lubricant to the test machine correlate well with performance of the 4 lubricant under actual work load conditions.

Although various lead and sulfur containing compositions are known to be useful as extreme pressure additives, identification of a lubricant formulation having sufficiently improved extreme pressure lubricating properties for commercial desirability is a difficult and highly empirical task. Thus, by far the great bulk of available additives and additive combinations which improve the Timken values of a lubricating grease do so to too minor a degree to justify the increased cost of the formulation. We have discovered that exceptionally high Timken values can be developed for extreme pressure lubricating grease by incorporation of a lead soap of sulfurized tall oil and a small, apparently catalytic, amount of an organic polysulfide such as dodecyl pentasulfide. For optimum results, a second oil miscible lead soap should be added in sufiicient amounts to provide a lead to sulfur ratio of approximately 3:1 or somewhat higher. For example, a lithium hydroxy stearate grease containing 5 weight percent of lead sulfurized tallate, 0.1 weight percent dodecyl pentasulfide and 1.5 weight percent of lead fish oil soap was found consistently to give passing Timken values of 50 to 55 pounds compared to 40 pounds for the best available competitive product known to us.

In formulating the extreme pressure lubricating greases of our invention, about 1 to 20 percent by weight of the lead soap of sulfurized tall oil may be used, but we have obtained best results in using about 5 percent of a 50 percent s'oil blend giving a lead content of approximately 05 weight percent in the finished grease composition. About 0.1 to 2 weight percent dodecyl pentasulfide may be employed although we prefer to use about 0.1 percent since the polysulfide tends to be corrosive in large amounts. Other polysulfides have value, provided they are suitably oil soluble. For example, diisooctyl polysulfides such as the pentasulfides, and other oil-soluble organic polysulfides produced by sulfurization of mercaptans may be employed. Of the alkyl mercaptans, those of 8 to 13 carbon atoms are believed to be most useful, but the number of carbon atoms in the organic group may vary from 6 to 20. Cyclic polysulfides including alicyclic and aromatic types may be used. Phenyl polysulfide, for example, has value.

The ratio of lead to sulfur in the finished grease is adjusted with advantage to about 3;1 by addition of a 2,790,770 Patented Apr. 30, 1957 soluble lead soap, advantageously the lead soap of fish oil. Other lead soaps such as lead naphthenate, lead stearate, lead oleate and the like may be used, but lead soaps of organic acids containing unsaturation are preferred. Although about 3:1 appears to give best results, the ratio may be varied over the range of about 2:1 to 4:1.

The effectiveness of the additive combination applies in general to soap thickened lubricating grease compositions. We have found, however, that incorporation of the additive combination in lithium greases, particularly of the lithium hydroxy stearate type, has particular advantages in both load bearing properties and multipurpose utility. The additive combination may be added with value to soap thickened greases of the usual types, for example, sodium, lime or barium soap greases and the like. The soap content of the base grease may vary from about 2 percent to about 25 percent by weight. The organic portion of the soap may be derived from one of the usual sources such as tallow, hydrogenated castor oil, 12-hydroxy stearic acid and the like. The oil base for the grease may comprise any suitable oleaginous vehicle, for example, a refined lubricating oil fraction having a viscosity in the range of about 50 S. S. U. at 100 F. to about 300 S. S. U. at 210 F.

The additives may be added to a finished grease stock, but in practice, it is usually desirable to incorporate the additives in the grease base during its initial manufacture, preferably at a temperature of upwards of about 220 F. The following data illustrate the eifectiveness of the additive combination of. the invention in imparting improved extreme pressure lubricating properties to a number of sample greases.

For the examples, the lead sulfurized tallate was prepared by the following procedure: Distilled tall oil (Indusoil) was heated at 330 F. with 10 percent of its weight of sulfur until a copper strip of 2-3 was obtained on heating at 250 F. for 1 hour. This required about 12 hours. The product contained about 9 percent of sulfur and had an acidity of 170 mg. KOH/gm. The lead soap was prepared as follows: 200 gms. of sulfurized tall oil, 10 ml. of butyl Cellosolve and 150 cc. of hot water were efiiciently stirred and warmed to 175 F. Lead oxide (67 gms.) was then gradually added. The reaction was considered complete when the lead oxide had disappeared (3 to 4 hours). The Water was drained and the product blown dry with air. The finished product contained approximately 20 percent lead and 6 percent sulfur. It was diluted to obtain a 50 percent oil concentrate containing 9.7 percent lead and 4.15 percent sulfur.

The organic polysulfide used in the examples was ditertiary dodecyl pentasulfide prepared by sulfurization of dodecyl mercaptan. Enough sulfur was added to t-do decyl mercaptan to provide 35 to 40 percent sulfur in the finished pentasulfide. The reaction was conducted at room temperature in the presence of a catalytic amount of alcoholic potash, e. g. 5 percent, for 3 to 4 hours. After removal of catalyst by settling, the product was washed with water.

The lead fish oil soap was made by the procedure described in U. S. Patent 1,830,984 and contained the following ingredients: 28 pounds menhaden oil, 22 pounds litharge and 50 pounds petroleum oil to S. S. U. at 1 The grease used for test purposes was prepared by neutralizing 6.3 pounds of 12-hydroxy stearic acid with 0.91 pound of lithium hydroxy mono-hydrate in a solvent extracted SAE-20 lubricating oil at 40% soap concentration. The neutralization was conducted at a temperature of about 200 F., and the reaction mixture was dehydrated by raising the temperature gradually to about 400 F. The mixture was allowed to cool while adding oil,

until 93.36 pounds of oil were contained in the mixture, and about 0.2 pound of an anti-oxidant (phenylene amine type). After cooling to about, 200-250 F., the grease was milled and deaerated. The extreme pressure additives were added to the resulting ease byheating. to a temperature of about 250 F; and rehomogenizing. The test data on the grease examples. are tabulatedbelow.

Lead Timkcu Test Soap of Y LeadFish Dodecyl Test No. Sulf. Tall Oil Soap Hexasul Oil fide 0. K. Scar Load 160 F. The resulting grease had the following formula:

Percent Calcium fatty acid soap 10.8 Water 1.1 Lead soap of sulfurized tall oil 3.0 Lead fish oil soap 1.0 Dodecyl pentasulfide 0.1 Asphaltic black oil of 118 S. S. U. at 210 F 83 The grease had an unworked penetration (ASTM) of 337 and a worked penetration of 332. It passed the Timken test at a test load of 40 pounds, failing at pounds, an excellent value for this type of grease.

We claim:

1. A lubricating grease composition which essentially comprises an oleaginous base thickened by a metal soap grease thickener, a lead soap of sulfun'zed tall oil, an oil soluble organic polysulfide and a second oil miscible lead soap in an amount increasing the ratio of lead to sulfur in the composition to the range of about 2:1 to 4:1.

2. A lubricating grease composition which essentially comprises an oleaginous base thickened by a metal soap grease thickener, about 2 to 20 weight percent of a lead soap of sulfurized tall oil, about 0.1 to 2 weight percent of an oil soluble organic polysulfide and a second oil miscible lead soap in an amount increasing the ratio of lead to sulfur in the composition to the range of about 2:1 to 4: 1.

3. The composition of claim 2 in which the organic polysulfide is adodecyl pentasulfide.

4. The composition of claim 2 in which the second lead soap is lead fish oil soap.

5. The composition of claim 2 in which the soap is a lithium soap.

6. The composition of claim 5 in which the lithium soap is a lithium hydroxy stearate. 7. The composition of claim 2 in which the soap is a calcium soap.

8. The composition of claim 2 in which the soap is a barium soap.

9. The composition of claim 2 in which the ratio of lead to sulfur is about 3:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,110,281 Adams Mar. 8, 1938 2,233,203. Flaxman Feb. 25, 1941 2,252,087. McNab Aug. 12, 1941 2,576,031 Morway Nov. 20, 1951 2,614,079 Moore Oct. 14, 1952 2,666,744 Dixon Jan. 19, 1954 

1. A LUBRICATING GREASE COMPOSITION WHICH ESSENTIALLY COMPRISES AN OLEAGINOUS BASE THICKENED BY A METAL SOAP GREASE THICKENER, A LEAD SOAP OF SULFURIZED TALL OIL, AN OIL SOLUBLE ORGANIC POLYSULFIDE AND A SECOND OIL MISCIBLE LEAD SOAP IN AN AMOUNT INCREASING THE RATIO OF LEAD TO SULFUR IN THE COMPOSITION TO THE RANGE OF ABOUT 2:1 TO 4:1. 